Multi-stage hybrid evaporative cooling system

ABSTRACT

A multi-stage hybrid evaporative cooling system is described as having a direct evaporative cooling subsystem and an indirect evaporative cooling subsystem having one of a horizontal and a vertical set of heat exchanger channels. The multi-stage hybrid evaporative cooling system with a horizontal set of heat exchanger channels has a portion of the horizontal heat exchanger channels partially extended into a next stage of the multi-stage system. The multi-stage hybrid evaporative cooling system with the vertical set of heat exchanger channels includes a first set of vertical set of heat exchanger channels spanning a substantial vertical height of the stage of the hybrid evaporative cooling system, and a second set spanning approximately half the height of the stage. The multi-stage hybrid evaporative cooling system further includes a refrigeration system for lowering the temperature of the indirect evaporative cooling subsystem air without affecting its pressure flow.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a method and apparatus for cooling systemsand, more particularly, to a multi-stage hybrid evaporative coolingsystems.

(2) Description of Related Art

The power degradation curves of most power generating systems are suchthat as the temperature of air increases, the output power of thesepower systems decreases due to a decrease in the density of the air. Inother words, most power generating systems require an intake of denseair for a more efficient operation in terms of greater power output.That is, the denser the air, the greater the operating efficiency of thepower generators. It is well known that cooler air is denser than warmerair, and hence, today's power generating intake systems are generallycoupled with air cooling systems, which provide the power generatingunits with cooler, and hence, more denser air for a more efficientoperation of the power units. Therefore, it could be said that thecooling systems indirectly function as power augmentation systems forpower generating systems by increasing their efficiency, and hence,their output power.

Traditional methods for providing cooler denser air to increase overallpower generating efficiency include steam injection, refrigeration,fogging, and direct evaporative cooling of air. A less expensiveapproach to increasing the intake air density by cooling, other thanthese conventional methods, is an indirect evaporative approach. Priorpatents in this area include Schlom et al.: U.S. Pat. Nos. 4,023,949;4,107,940; 4,137,058; 4,156,351 and 4,418,527; Fogelman: U.S. Pat. No.5,076,347; and Kopko: WO9851916A1.

A recently developed method for cooling air is the hybrid evaporativecooling system (known as the “Schlom” cycle) disclosed in the U.S. Pat.No. 6,385,987 to Schlom et al., which may be used as standalone aircooler or with different power generating systems. The entire disclosureof the U.S. Pat. No. 6,385,987 to Schlom et al, issued May 14, 2002, isincorporated herein by this reference, and the information incorporatedherein is as much a part of this application as filed as if the entiretext and drawings of the U.S. Pat. No. 6,385,987 were repeated in thisapplication, and should be treated as part of the text and drawings ofthis application as filed.

The heat exchangers disclosed in U.S. Pat. No. 6,385,987 are useful forboth single and multiple unit indirect evaporative processes. Theevaporative apparatus for cooling comprises both a multi-stage indirectevaporative cooling heat exchanger, and a multi-stage sump where eachsump stage, in a one-to-one relationship with a stage of the multi-stageheat exchanger has sump water at progressively cooler temperatures asair progresses further into the heat exchanger. Because there areseparate, and completely sealed and isolated stages of the heatexchanger and the water sumps (creating thermal isolation between thestages), progressive cooling is induced on dry side output air. Othermultistage heat exchangers with their associated multistage sumps can becombined, with the cooled air of a first multistage evaporative assemblyfeeding into the intake end of a second multistage evaporative assembly,and so on, with each sealed stage of the multistage assembly beingthermally isolated.

Areas in which additional increased efficiency of the hybrid evaporativecooling system disclosed in the U.S. Pat. No. 6,385,987 might beimproved include a better heat exchange and coolant evaporationprocesses, and the use of a novel refrigeration processes, bringing the“room” inlet dry-bulb temperature as close as possible to the exhaustair wet-bulb temperature so as to increase the thermodynamic efficiencyof the actual process.

BRIEF SUMMARY OF THE INVENTION

The present invention provides and uses improved heat exchange, coolantevaporation, and novel refrigeration processes to improve the efficiencyof a multi-stage hybrid evaporative cooling system.

One aspect of the present invention provides a multi-stage hybridevaporative cooling system, comprising:

a direct evaporative cooling subsystem within a stage of the multi-stagehybrid evaporative cooling system;

an indirect evaporative cooling subsystem within the stage of themulti-stage hybrid evaporative cooling system, with a portion of theindirect evaporative cooling subsystem within the stage of themulti-stage hybrid evaporative cooling system partially extending into anext stage thereby facilitating a further cooling of the next stagedirect evaporative cooling subsystem.

One optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the direct evaporative cooling subsystem is comprised of a sump withinthe stage of the multi-stage hybrid evaporative cooling system forholding a coolant that is provided to a set of heat exchangers withinthe stage of the multi-stage hybrid evaporative cooling system by a pumpthat moves the coolant to a distribution manifold for delivery of thecoolant on to the heat exchangers, wherein a direct evaporative coolingsubsystem airflow evaporates the coolant flowing down an exteriorsurface of the heat exchanger for indirect evaporative cooling of anindirect evaporative cooling subsystem airflow.

Another optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the direct evaporative cooling subsystem generates a latent heat ofevaporation, which causes a conductive heat transfer for the indirectevaporative cooling subsystem at a lower temperature, thereby loweringan indirect evaporative cooling subsystem airflow.

Yet another optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the direct evaporative cooling subsystem is comprised of:

an exhaust unit in the stage of the multi-stage hybrid evaporativecooling system for exhausting a direct evaporative cooling subsystemairflow from the direct evaporative cooling subsystem; and

a moisture eliminator in the stage of the multi-stage hybrid evaporativecooling system for removing coolant droplets from the direct evaporativecooling subsystem airflow prior to exhausting the direct evaporativecooling subsystem airflow from the direct evaporative cooling subsystem.

A further optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the exhausted direct evaporative cooling subsystem airflow is directedto external systems for cooling of the external systems.

Still a further optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the direct evaporative cooling subsystem is comprised of:

an exhaust unit for exhausting a direct evaporative cooling subsystemairflow from the direct evaporative cooling subsystem; and

a moisture eliminator in the stage of the multi-stage hybrid evaporativecooling system for removing coolant droplets from the direct evaporativecooling subsystem airflow prior to exhausting the direct evaporativecooling subsystem airflow from the direct evaporative cooling subsystem.

Another optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the coolant within the sump of a final stage of the multi-stage hybridevaporative cooling system is provided to a media pump, moving thecoolant to a distribution system for distributing coolant along a top ofa media for further cooling and washing the indirect evaporative coolingsubsystem airflow.

Yet another optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the coolant from the media further lowers the temperature of theindirect evaporative cooling subsystem air flow due to furtherevaporation of the coolant; and

the further evaporation of the coolant results in a lower dry bulbtemperature, causing a further reduction of the temperature of thecoolant in a media sump, which when drained into the final stage sump,reduces a temperature of the coolant present within the final stagesump.

A further optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the direct evaporative cooling subsystem is comprised of:

-   -   a refrigeration unit for further cooling of the direct        evaporative cooling subsystem air.

Still a further optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

a condenser coil of the refrigeration unit is positioned along a path ofa direct evaporative cooling subsystem airflow.

Another optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the refrigeration unit is comprised of:

an expansion device for expanding a liquid refrigerant into a lowtemperature vapor refrigerant;

an evaporator-chiller for lowering a coolant temperature using the lowtemperature vapor refrigerant from the expansion device;

a compressor for compressing the low temperature vapor refrigerant fromthe evaporator-chiller to a high temperature gaseous refrigerant due toheat of compression; and

a condenser coil for cooling the high temperature gaseous refrigerantfrom the compressor into a medium temperature liquid refrigerant, andfed to the expansion device.

Yet another optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

a coolant from a first stage sump of one or more stages is moved by apump into the evaporator-chiller for lowering a temperature of thecoolant, and is moved to a last stage sump of one or more stages;

whereby excess coolant in the last stage sump is cascaded down to apreceding stage sump, thereby lowering coolant temperature of thepreceding stage sump.

A further optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the heat exchangers are comprised of a separate set of plates to formseparate heat exchangers for a stage, with independently created heatexchangers within each stage aligned to form continuous channels for anairflow of the indirect evaporative cooling subsystem air from one stageto the next.

Another optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the heat exchangers are comprised of an upper set of plates that span anentire horizontal length of all the stages of the hybrid evaporativecooling system, and a lower of plates that partially span an entirehorizontal length of each stage, with both the upper and the lower setof any subsequent stage heat exchangers being an extension of apreceding stage heat exchangers.

Another aspect of the present invention provides a multi-stage hybridevaporative cooling system, comprising:

an indirect evaporative cooling subsystem within a stage of themulti-stage hybrid evaporative cooling system;

a direct evaporative cooling subsystem within the stage of themulti-stage hybrid evaporative cooling system, with a first portion ofthe direct evaporative cooling subsystem substantially extending avertical length of the stage, and a second portion partially extendingthe vertical length of the stage, thereby facilitating a further coolingof a next stage indirect evaporative cooling subsystem.

Another optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the indirect evaporative cooling subsystem includes an indirectevaporative cooling subsystem enclosure for preventing an interchange ofindirect evaporative cooling subsystem air pattern and directevaporative cooling subsystem air pattern, the indirect evaporativecooling subsystem enclosure, comprising:

a top header for preventing flow of a coolant to within the indirectevaporative cooling subsystem enclosure;

at least one divider for maintaining separation between indirectevaporative cooling subsystem airflows;

a bottom header for preventing flow of a direct evaporative coolingsubsystem air to within the indirect evaporative cooling subsystemenclosure.

Yet another optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the at least one divider separates the stage of the multi-stage hybridevaporative cooling system into two or more horizontal sections formaintaining separation between indirect evaporative cooling subsystemairflows, thereby allowing the indirect evaporative cooling subsystemairflows through a first of the two or more horizontal sections to exitout of the indirect evaporative cooling subsystem enclosure and into thedirect evaporative cooling subsystem, and allowing indirect evaporativecooling subsystem airflows through a second of the two or morehorizontal sections to continue into the indirect evaporative coolingsubsystem enclosure within a next stage.

A further optional aspect of the present invention provides amulti-stage hybrid evaporative cooling system, wherein:

the direct evaporative cooling subsystem is comprised of a sump withinthe stage of the multi-stage hybrid evaporative cooling system forholding a coolant that is provided to a set of heat exchangers withinthe stage of the multi-stage hybrid evaporative cooling system by a pumpthat moves the coolant to a delivery manifold for delivery of thecoolant within the heat exchanger channels, wherein a direct evaporativecooling subsystem airflow within the heat exchanger channels evaporatesthe coolant flowing down within the heat exchanger channels for indirectevaporative cooling of an indirect evaporative cooling subsystem airflowexterior to the heat exchanger channels.

Another optional aspect of the present invention provides a multi-stagehybrid evaporative cooling system, wherein:

the heat exchangers are comprised of a set of plates forming a verticalset of heat exchanger channels;

with a first set of vertical set of heat exchanger channels spanning asubstantial height of the stage of the hybrid evaporative coolingsystem, and a second set of the vertical set of heat exchangers channelsspanning approximately half the height of the of the hybrid evaporativecooling system.

These and other features, aspects, and advantages of the invention willbe apparent to those skilled in the art from the following detaileddescription of preferred non-limiting exemplary embodiments, takentogether with the drawings and the claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

It is to be understood that the drawings are to be used for the purposesof exemplary illustration only and not as a definition of the limits ofthe invention. Throughout the disclosure, the word “exemplary” is usedexclusively to mean “serving as an example, instance, or illustration.”Any embodiment described as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other embodiments.

Referring to the drawings in which like reference character(s) presentcorresponding parts throughout:

FIG. 1 is an exemplary illustration for an embodiment for a multi-stagehybrid evaporative cooling system in accordance with the presentinvention;

FIG. 2 is an exemplary schematic illustration for a set of cascadedsumps for an exemplary three stage system for a multi-stage hybridevaporative air-cooling system in accordance with the present invention;

FIG. 3 is an exemplary illustration for another embodiment for amulti-stage hybrid evaporative cooling system in accordance with thepresent invention;

FIG. 4 is an exemplary schematic section of an N-stage (the first fiveof the six stages are shown) for a multi-stage hybrid evaporativecooling system in accordance with the present invention;

FIG. 5 is an exemplary illustration for another embodiment for amulti-stage hybrid evaporative cooling system in accordance with thepresent invention, which uses a novel refrigeration process to augmentcooling processes;

FIG. 6 is an exemplary schematic perspective view for yet anotherembodiment for a multi-stage hybrid evaporative cooling system inaccordance with the present invention; and

FIG. 7 is an exemplary illustration of the multi-stage hybridevaporative cooling system of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an exemplary illustration for an embodiment for a multi-stagehybrid evaporative cooling system 100 in accordance with the presentinvention that may be used as a standalone or with different powergenerating systems. As illustrated, system 100 is comprised of an airintake housing 102, one or more different isolated cooling chambers orstages (only two stages (#1 and #2) are shown), and an air dischargehousing 104. The pluralities of different stages are isolated, with eachstage comprised of a direct evaporative cooling subsystem and anindirect evaporative cooling subsystem. The sizes of each stage may varybased upon the thermal exchange capacity of each stage and the overallsystem.

Each stage within the multi-stage hybrid evaporative cooling system 100is completely sealed from the next successive stage to isolate thewet-bulb temperature of one stage from a subsequent stage. The system100 includes a set of heat exchangers for each stage, which aregenerally comprised of plates that are arranged in pairs to formcontinuous horizontal channels from one stage to the next subsequentstage for airflow. The interior of the continuous horizontal channelsfor the airflow is where the indirect evaporative cooling processes takeplace. In other words, conductive heat transfer takes place within theheat exchanger channels between the indirect evaporative coolingsubsystem airflow and the interior walls of the heat exchanger channelsto cool the air flowing within the channels. The exterior of thesehorizontal heat exchanger channels is where the direct evaporativecooling processes occur. FIG. 1 shows a schematic section of only atwo-stage version for the multi-stage hybrid evaporative cooling system100 of the present invention, showing various airflow paths.

The multi-stage hybrid evaporative cooling system 100 illustrated inFIG. 1 may be coupled with a power generating unit (not shown), with thecooler dense (or useful) air (from the indirect evaporative coolingsubsystem of the system 100) fed to an intake unit of a power generatingsystem. As illustrated, ambient air 110 is pulled into the system 100through the air intake housing 102, passing an air intake unit 106, anair intake filter 108, and into the first stage heat exchangers 112 asindirect evaporative cooling subsystem airflow 114. As described above,the first stage heat exchangers 112 are generally comprised of platesthat are arranged in pairs to form continuous horizontal channels fromone stage to the next subsequent stage, within which the indirectevaporative cooling subsystem air 114 flows. The indirect evaporativecooling subsystem airflow 114 is the air that is maintained dry,progressively cooled down at each stage as it moves through thecontinuous horizontal heat exchanger channels that extend to the nextsubsequent stage, and exhausted through the air discharge housing 104.Optionally, the exhausted airflow 116 may be subsequently used by theintake system of a power-generating unit as a cooler, denser air.

The ambient air 110 is also pulled into system 100 through a lower airintake opening 118 and into the direct evaporative cooling subsystem asairflow 119. The direct evaporative cooling subsystem airflow 119 passesover a first stage sump 120, and is subsequently drawn up (illustratedas the two straight, vertical up arrows), and exhausted out (referencedas 122) into the atmosphere by the first stage direct evaporativecooling subsystem fan 124. The first stage sump 120 further includes afirst stage pump 126 that moves coolant stored within the first stagesump 120 through a first stage tube 128 to a first stage coolantdistribution manifold 130. The coolant distribution manifold 130 iscomprised of one or more nozzles or other coolant delivery mechanisms132 through which coolant (such as water) is sprayed or delivered byother means, and cascades down the exterior portion of the first stageheat exchangers 112 to cool down the heat exchanger. The directevaporative cooling subsystem airflow 119 (or wet airflow) moving up thefirst stage of system 100 contacts the cascading coolant (and hence theterm “wet airflow”), and facilitates the evaporation of the cascadingcoolant. This evaporation directly cools the interior ambient air ofstage #1 within the direct evaporative cooling subsystem, and indirectly(through latent heat of evaporation) cools the dense or useful airflow114 within the channels of the first stage heat exchangers 112. In otherwords, the wet side airflow 119 within the first stage causes the directevaporation of the coolant, and the dry side airflow 114 is cooledindirectly by this evaporation through conductive heat transfer bycoming into contact with the interior walls of the heat exchangerchannels.

The drawn up wet airflow 122 move up by the first stage directevaporative cooling subsystem fan 124, with coolant droplets impingingupon a first stage moisture eliminator element 134, which filters outmost of the droplet moisture from the airflow 119 prior to exhaustion.Therefore, the remaining exhausted airflow 122 is generally air withhigh humidity (assuming the coolant is water) with no droplets, and thefiltered-out coolant droplets that are impinged upon the moistureeliminator filter 134 simply drain down back into the first stage sump120. Accordingly, the coolant is recycled and the first stage motor fan124 remains fairly dry. In addition, moist wet airflow 119 is not fedback into the atmosphere, proximal to the air intake housing 102 of theindirect evaporative cooling subsystem of the multi-stage hybridevaporative cooling system 100. Coolant 117 may be replenished through acoolant inlet 136 as described below in relation to FIG. 2.

The exhausted, cool, direct evaporative cooling subsystem airflow 122may be used to cool the temperature of other systems. For example, thecool airflow 122 may be used to cool down generator and or turbinerooms, including lubrication oil used by other external systems.Conventionally, prior art systems use large size fans for cooling. Thisuse of cooler airflow 122 can eliminate the need for large sized fans.Instead, using the already cooled airflow 122, smaller sized fans can beused to cool the ambient temperature with the in flow of cooler air 122,saving on the energy expenditure used for operating the larger fans.Accordingly, the exhausted moist airflow 122 may be used for coolingdown generator and or turbine rooms, including lubrication oil used byother external systems, and the exhausted dense airflow 116 may be usedby the intake system of a power-generating unit as a cooler, denser airfor a more efficient operation.

The present invention uses the thermodynamic relationship between latentheat and sensible (conductive) heat for a more efficient cooling of theindirect evaporative cooling subsystem airflows 114 in the first stageand air 121 in the second stage. That is, the multi-stage hybridevaporative cooling system 100 uses the relationship between the heatthat is associated with a change in temperature (sensible heat) incontrast to a heat interchange associated with a change of state (latentheat). Latent heat is the heat that is either released or absorbed by aunit mass of a substance when it undergoes a change of state (a phasechange), such as during evaporation, condensation, or sublimation, butnot its temperature (e.g., the coolant within the system 100 at orduring the change of phase remains the same temperature). In thisinstance, when the coolant evaporates within the first stage, it absorbsheat from within that stage to evaporate, and hence, the coolant changesits state, and this absorbed heat from the ambient air of the system 100reduces the ambient temperature within the stage to decrease thesensible heat.

The sensible heat is one that can be felt, sensed, or detected, by achange in the temperature of the system. Sensible heat is the heatabsorbed or transmitted when the temperature of a substance changes, butthe substance does not change state. It is the conductive heat added orsubtracted that causes a change in temperature. The evaporation of thecoolant absorbs ambient heat, causing a reduction (subtraction) in thesensed temperature (sensible heat) at the first stage heat exchanges112, cooling down indirect evaporative cooling subsystem airflows (oruseful) air 114 within the first stage and 121 within the second stageinside the channels of the respective heat exchanger 112 and 140 throughconductive heat transfer.

In terms of molecular interplay, the coolant changes from a liquid to avapor state, which requires a gain of molecular kinetic energy. Thisgain of molecular kinetic energy is at the expense of the remainingcoolant, which loses that same amount of energy, expressed as the latentheat of evaporation. Thus, the temperature of the un-evaporated coolantand the first stage heat exchange surfaces in contact with it reflectsome decrease in their molecular kinetic energy (conservation ofenergy). The reduced molecular kinetic energy is expressed as adecreased sensible heat, which reduces the temperature of the indirectevaporative cooling subsystem air 114 and 121 through conductive heattransfer.

As further illustrated in FIG. 1, the second stage heat exchangers arecomprised of an upper set of second stage heat exchangers 140 that spana full horizontal length of the second stage, and a lower set of secondstage heat exchanges 142 that partially extend the full horizontallength of the second stage. As with the first stage heat exchangers 112,both sets of the second stage heat exchangers 140 and 142 are generallycomprised of plates that are arranged in pairs to form continuoushorizontal channels from one stage to the next subsequent stage forindirect evaporative cooling subsystem airflow. Therefore, the indirectevaporative cooling subsystem air 114 flowing from the first stage heatexchanger channels continuously flows through the channels of the upperset of the second stage heat exchanger 140 as a much cooler air 121 andis exhausted through the air discharge housing 104. The indirectevaporative cooling subsystem air 114 flowing from the first stage heatexchanger channels also continuously flows through the channels of thelower set of the second stage heat exchanger 142 and is exhausted intothe second stage, which becomes a much cooler direct evaporative coolingsubsystem air 144.

In one embodiment, the heat exchangers within each stage may becomprised of a separate set of plates to form separate heat exchangersfor a stage, so long as the heat exchangers that are independentlycreated within each stage are aligned to form continuous horizontalchannels for the airflow of the indirect evaporative cooling subsystemair from one stage to the next. In another embodiment, the first stageplates of the first stage heat exchangers may span the entire length ofall the stages of the multi-stage hybrid evaporative cooling system 100.In this case, both the upper and the lower set of any subsequent stageheat exchangers would be mere extension of the preceding stage heatexchangers. However, regardless of the embodiment used to form the heatexchangers, the present invention provides for a lower set of heatexchangers that do not fully extend or span across the entire horizontallength of any one particular stage (or a subsequent stage thereof), butare only partially extended across the horizontal length of a stage.

As illustrated in FIG. 1, some of the indirect evaporative coolingsubsystem (dry side) airflow 114 within the channels of the first stageheat exchangers 112 is exited and redirected out of the lower set of thesecond stage heat exchangers 142, and into the direct evaporativecooling subsystem as second stage direct evaporative cooling subsystemair 144. The second stage direct evaporative cooling subsystem airflow144 is cooler than the preceding stage airflow 119 because the secondstage direct evaporative cooling subsystem airflow 144 has already gonethrough the first stage heat exchangers 112 as air flow 114, andtherefore, has been substantially cooled. In addition, in accordancewith the present invention, the second stage direct evaporative coolingsubsystem airflow 144 has also traversed the lower set of the secondstage heat exchangers 142, which are cooler than the first stage heatexchangers 112, the reasons for which are described below. Therefore,the airflow exiting out of these particularly lower set of heatexchangers 142 is in fact cooler than the airflow in the preceding stagechannels of the heat exchangers 112.

The lower set of any subsequent stage heat exchangers furtherfacilitates the evaporation of a lower temperature cascading coolant totake place on the outside surfaces of these lower set of heat exchangerswith a lower wet bulb temperature air. This causes further reduction inthe temperature of the indirect evaporative cooling subsystem airexiting through, and out into the subsequent stage. More specifically,and in relation to FIG. 1, the lower set of the second stage heatexchangers 142 allows further evaporation of coolant at even lowertemperature to take place on the outside surfaces of the lower set ofthe second stage heat exchangers 142. This causes a further reduction intemperature of the indirect evaporative cooling subsystem airflow 114before it emerges out into the direct evaporative cooling subsystem ofthe next subsequent stage (the second stage), as direct evaporativecooling subsystem air 144.

In general, the lower set of any subsequent stage heat exchangers have alength of approximately equal to about one-half the horizontal length ofa stage. The actual number of channels that constitute a height of thelower set of any subsequent stage heat exchangers is generally equal toor less than the number of channels of the fully extended upper channelsof the upper set of the second stage heat exchangers within which thelower set terminates. That is, the number of channels of the lower setof any subsequent stage heat exchangers is equal to or less than thenumber of channels that constitute the upper set of any subsequent stageheat exchanges.

The much cooler direct evaporative cooling subsystem air 144 at thesecond stage passes over a second stage sump 150, and is subsequentlydrawn up and drawn out (referenced as 152) into the atmosphere by asecond stage direct evaporative cooing subsystem fan 154. The secondstage sump 150 further includes a second stage pump 156 that movescoolant stored within the second stage sump 150 through a second stagetube 158 to a second stage coolant distribution manifold 160. The secondstage coolant distribution manifold 160 is comprised of one or morenozzles or other coolant delivery mechanisms 162 through which coolant(such as water) is sprayed or delivered by other means, and cascadesdown the exterior portion of the upper and lower set of second stageheat exchangers 140 and 142 to cool down the channels of the upper andlower heat exchanger of the second stage. The second stage directevaporative cooling subsystem airflow 144 (or wet airflow) moving up thesecond stage of system 100 contacts the cascading coolant, andfacilitates the evaporation of the cascading coolant. This evaporationdirectly cools the interior ambient air of stage #2 within the directevaporative cooling subsystem, and indirectly cools the dense or usefulairflow 121 within the upper and lower set of the second stage heatexchangers 140 and 142. In other words, the wet side airflow within thesecond stage causes the direct evaporation of the coolant, and the denseside airflow 121 is cooled indirectly by this evaporation throughconductive heat transfer between itself and the interior walls of theheat exchanger channels. The direct evaporative cooling subsystem air144 moving up the second stage facilitates the further evaporation ofthe cascading coolant at even lower temperature on the surfaces of thesecond stage heat exchangers 140 and 142. This evaporation directlycools the ambient air (due to latent heat of vaporization) within thesecond stage of the system 100 further, and indirectly further cools theindirect evaporative cooling subsystem air 121 flowing within both theupper and lower set of second stage heat exchangers 140 and 142 throughconductive heat transfer.

The drawn up wet airflow 152 move up by the second stage directevaporative cooling subsystem fan 154, with coolant droplets impingingupon a second stage moisture eliminator element 164, which filters outmost of the droplet moisture from the airflow prior to exhaustion.Therefore, the remaining exhausted airflow 152 is generally air withhigh humidity (assuming the coolant is water) with no droplets, and thefiltered-out coolant droplets that are impinged upon the second stagemoisture eliminator filter 164 simply drains down back into the secondstage sump 150. Accordingly, the coolant is recycled and the secondstage motor fan 154 remains fairly dry. In addition, moist wet airflow144 is also not fed back into the atmosphere, proximal to the air intakehousing 102 of the indirect evaporative cooling subsystem of themulti-stage hybrid evaporative air-cooling system 100. As with theexhausted cool air 122 of the first stage #1, the exhausted, cool,direct evaporative cooling subsystem second stage airflow 152 may beused to cool the temperature of other systems.

The two-stage version of the multi-stage hybrid evaporative coolingsystem 100 is secured on a base 170 that spans its entire length, andsupports the two separated sumps 120 and 150 for each respective stage.Coolant is sprayed or delivered by other mechanisms by the respectivedistribution manifolds 130 and 160 of each stage, and is cascaded downthe respective heat exchangers 112, 140 and 142 into the respectivesumps 120 and 150. Therefore, a feature of the multi-stage hybridevaporative cooling system 100 is that it provides for a portion of theindirect evaporative cooling subsystem air 114 to be first indirectlyevaporatively cooled and then used as direct evaporative coolingsubsystem air for the next successive stage.

As further illustrated, the second stage (and in general), the finalstage of any multi-stage hybrid evaporative cooling system 100 furtherincludes a media pump 172 that moves coolant from a final stage sump (inthis case sump 150) through a media tube 174 into the air dischargehousing 104. The media pump 172 moves the coolant within the final stagesump 150 to a distribution system for distributing the coolant along atop of a primary media 176 and a secondary media 178 for further coolingand washing the indirect evaporative cooling subsystem airflow 121 as itenters the discharge housing 104 as air 123. Both the primary media 176and the secondary media 178 include respective primary cover washer 180and a secondary cover washer 182 for forcing the coolant downwardstowards the respective primary and the secondary media 176 and 178. Thecoolant cascading down the primary and the secondary media 176 and 178is collected into a media sump 183, where the coolant 185 is drainedthrough a media sump outlet 184, and back into the final stage sump 150.The coolant cascading down the medias further lowers the temperature ofthe airflow 123 flowing within the air discharge housing 104, where itis exhausted as airflow 116. The reason for further cooling of theairflow 121 as it enters and passes through the air discharge housing104 as the cooler air 123 is due to further evaporation of the coolantwithin the discharging housing 104. In addition, the further evaporationof the coolant results in lower dry bulb temperature within thedischarge housing 104, causing a further reduction of the temperature ofthe coolant in media sump 183, which when drained into the final stagesump 150, reduces the temperature of the coolant present within thefinal stage sump 150.

FIG. 2 illustrates a schematic section of a set of cascaded sumps for anexemplary three stage system for a multi-stage hybrid evaporatingcooling system in accordance with the present invention. As illustrated,the present invention provides separate, distinct sumps 120, 150, and202 for the coolant used by the direct evaporative cooling subsystem onthe exterior surfaces of the heat exchangers. The separate sumpsmaintain the coldest coolant on the last stage of the multi-stage hybridevaporative cooling system 100. As illustrated, these sumps can bearranged in a “cascade” fashion where the coolant flows from the coldestfinal sump 202 within the last illustrated stage #3 to the warmest sump120 within the first illustrated stage #1.

A float valve 204 or any other coolant level regulating mechanismregulates the refilling of the coldest sump 202, as required, by thelevel of coolant in the warm-side sump 120. When the level in the sump120 falls, the float valve 204 allows coolant to enter from the coolantinlet 136. The coolant line 206 from the float valve 204 to the lastsump 202, allows the last sump to be refilled with coolant according tothe level of the first sump 120. Coolant transfer pipes 208 and anoverflow (and drain) pipe 210 complete the sump system.

Each separate sump sits at the bottom of separate delivery or spraysystems with separate pumps that supply each separate delivery mechanismand sump unit. In the preferred embodiment the last sump would be at theair washer, or, at the last heat exchanger, if a direct evaporativestage were not used. In this embodiment coolant is supplied to thedirect evaporative stage only and then flows down to the lowest sumpwhere any excess water is discharged. In addition, at this pointsufficient “bleed” will be employed to maintain a low concentration ofdissolved solids in the coolant to prevent the build-up of dissolvedsolids on the walls of the heat exchanger. Because the different sumpsare sufficiently thermally insulated, and the air progressing througheach partition or stage is tending to be cooler than the previous stageor partition, the temperature of the thermally graded sumps both reflectthis increased cooling and contribute to it. It should be noted that allcoolant within the hybrid multi-stage cooling system 100 of the presentinvention are passed through one or more filtering mechanisms forfiltering or removal of foreign objects or debris from coolant.

FIG. 3 is an exemplary illustration for another embodiment of amulti-stage hybrid evaporative cooling system 300, with a single directevaporative cooling subsystem fan 302 for use with one or more stages.Each stage of the multi-stage hybrid evaporative cooling system 300includes the same corresponding or equivalent components as each stageof the multi-stage hybrid evaporative cooling system 100 that is shownin FIGS. 1 and 2, and described above. Therefore, for the sake ofbrevity, clarity, and convenience the general description of FIG. 3 willnot repeat every corresponding or equivalent component that has alreadybeen described above in relation to the multi-stage hybrid evaporativecooling system 100 that is shown in FIGS. 1 and 2.

As illustrated in FIG. 3, the direct evaporative cooling subsystemairflow within any stage is drawn up, and exhausted out into theatmosphere by a single direct evaporative cooling subsystem fan 302. Thedrawn up wet airflows move up by the single direct evaporative coolingsubsystem fan 302, with coolant droplets within the airflow impingingupon a moisture eliminator elements of each stage, which filter out mostof the droplet moisture from the airflow prior to exhaustion. Therefore,the remaining exhausted airflow is generally air with high humidity(assuming the coolant is water) with no droplets, and the filtered-outcoolant droplets that are impinged upon the respective moistureeliminator filters within each stage simply drains down back into therespective stage sump of each stage. Accordingly, the coolant isrecycled and the single motor fan 302 remains fairly dry.

FIG. 4 shows a schematic section of an N-stage (the first five of thesix stages are shown) multi-stage hybrid evaporative cooling system 400.Each stage of the multi-stage hybrid evaporative cooling system 400includes the same corresponding or equivalent components as each stageof the multi-stage hybrid evaporative cooling system 100 that is shownin FIGS. 1 and 2, and described above. Therefore, for the sake ofbrevity, clarity, and convenience the general description of FIG. 4 willnot repeat every corresponding or equivalent component that has alreadybeen described above in relation to the multi-stage hybrid evaporativecooling system 100 that is shown in FIGS. 1 and 2.

As illustrated in FIG. 4, the incoming ambient air 110 enters theindirect evaporative cooling subsystem and ultimately exits as cool,dense air 116. The same ambient air 110 enters the direct evaporativecooling subsystem, and is then drawn up as airflow 119 by the directevaporative cooling subsystem fan 124 of the first stage. As with thetwo stage process that was illustrated in FIGS. 1 to 3 and describedabove, some of the indirect evaporative cooling subsystem air 114, 121,425, 427, and 431 at each stage is redirected into the directevaporative cooling subsystem at the next successive stages as air 144,402, 404, and 406. The air 144, 402, 404, and 406 traverse therespective lower set of the subsequent stage heat exchangers 142, 408,410, and 412, and therefore, the airflow exiting out of theseparticularly channels of heat exchangers becomes progressively cooler.In general, the lower set of the subsequent heat exchangers 142, 408,410, and 412 have a length approximately equal to about one-half thehorizontal length of each stage. The actual number of channels thatconstitute a height of the lower set of any subsequent stage heatexchanger is generally equal to or less than the number of channels ofthe fully extended upper channels for that stage. That is, the number ofchannels of the lower set of any subsequent stage heat exchangers isequal to or less than the number of channels that constitute the upperset of any subsequent stage heat exchanges.

The lower set of the subsequent stage heat exchangers 142, 408, 410, and412 further facilitate the progressive cooling of the indirectevaporative cooling subsystem air flow 114, 121, 425, 427, and 431. Theevaporation of lower temperature coolant within each successive stagetakes place on the outside surfaces of these extended heat exchangers ata progressively lower wet-bulb temperature air that is lower than thatof the previous stage. This cooler air evaporating a cooler coolantcascading on the lower set of the subsequent stage heat exchanger 142,408, 410, and 412 causes a further reduction in the temperature of theair 114, 121, 425, 427, and 431, progressing through each successivestage in the sequence. In other words, by extending the lower portion ofthe heat exchangers into the next stage, further evaporation at evenlower temperature takes place on the outside surfaces of the extendedchannels in the next sequential stage. This causes a further reductionin temperature of the indirect evaporative cooling subsystem airflow114, 121, 425, 427, and 431 before it emerges into the directevaporative cooling subsystem of the next sequential stage as airflow144, 402, 404, and 406. The cooler direct evaporative cooling subsystemairflows 144, 402, 404, and 406, in turn, further cool the indirectevaporative cooling subsystem airflow 114, 121, 425, 427, and 431flowing through the upper set of the subsequent heat exchangers withineach stage.

Consequently, the already cooled indirect evaporative cooling subsystem(dry side) air 114, 121, 425, 427, and 431 becomes the directevaporative cooling subsystem (wet-side) air 144, 402, 404, and 406 ateach successive stage, resulting in respective lower temperature wetside air 144, 402, 404, and 406 within each respective stage, having alower wet side dew point temperature. The overall effect is a moreefficient cooled dense air 116 that exits at even a lower temperatureair stream with a higher air density. The coldest coolant in the sump atthe final stage further cools the coldest indirect evaporative coolingsubsystem dry air 431 at stage 5 and the coldest wet side air 406 withthe lowest wet bulb temperature. The lower set of the subsequent stageheat exchangers 142, 408, 410, and 412 provide a greater efficiency interms of proving a lower dry bulb temperature, and therefore, improvingthe overall system efficiency. The respective fans 124, 154, 420, 422,and 426 of each stage exhaust all the direct evaporative coolingsubsystem airflows 119, 144, 402, 404, and 406 as respective exhaustairflows 122, 152, 430, 432, and 434.

As with the two stage system illustrated in FIGS. 1 to 3 and describedabove, the system 400 illustrated in FIG. 4 also includes spray or otherdelivery manifolds or other coolant distribution mechanisms receivingpumped coolant from their respective sumps within each stage, and arespective moisture eliminators. The drawn up wet airflow 119, 144, 402,404, and 406 move up by the respective direct evaporative coolingsubsystem fans 124, 154, 420, 422, and 426 with coolant dropletsimpinging upon the respective moisture eliminator elements, which filterout most of the droplet moisture from the airflows prior to exhaustion.Therefore, the remaining exhausted airflow 122, 152, 430, 432, and 434is generally air with high humidity (assuming the coolant is water), andthe filtered-out coolant droplets that are impinged upon the moistureeliminator filters simply drains down back into their respective stagesumps. Accordingly, the coolant is recycled and the motor fans remainfairly dry. In addition, moist wet airflows are not fed back into theatmosphere, proximal to the inlet of the indirect evaporative coolingsubsystem of the multi-stage hybrid evaporative air-cooling system 400.

FIG. 5 illustrates yet another embodiment for a multi-stage hybridevaporative cooling system 500 in accordance with the present invention,which uses a novel refrigeration process to augment the coolingprocesses. The refrigeration system illustrated and described herein maybe used with any of the embodiments disclosed. Each stage of themulti-stage hybrid evaporative cooling system 500 includes the samecorresponding or equivalent components as each stage of the multi-stagehybrid evaporative cooling system 100 that is shown in FIGS. 1 and 2,and described above. Therefore, for the sake of brevity, clarity, andconvenience the general description of FIG. 5 will not repeat everycorresponding or equivalent component that has already been describedabove in relation to the multi-stage hybrid evaporative cooling system100 that is shown in FIGS. 1 and 2.

As illustrated in FIG. 5, the multi-stage hybrid evaporative coolingsystem 500 includes a novel refrigeration system to further cool downthe direct evaporative cooling subsystem, in particular, by cooling theaccumulated coolant within the sump of each stage. Unlike mostconventional refrigeration units, the refrigeration system of thepresent invention does not place a cooling coil within the stream of theindirect evaporative cooling subsystem airflow 114 and 121 to cool theair stream that contacts or impinges it. Instead, the refrigerationsystem of the present invention uses the coolant that is circulatedthrough the direct evaporative cooling subsystem to indirectly cool theindirect evaporative cooling subsystem air stream 114 and 121.

The refrigeration system in accordance with the present inventioneliminates a considerable impediment to the flow of the indirectevaporative cooling subsystem air 114 and 121, which were caused by theuse of cooling coils (used in the prior art) that were placed directlyacross the stream of indirect evaporative cooling subsystem air flow 114and 121 to cool the air 114 and 121. This impediment to the airflowreduced the inlet pressure factor, thereby reducing the power out of apower generating system. The airflow pressure factor is the resistanceof the airflow, which is measured in inches of water. Therefore, just aswhen the temperature increases and the power output of the powergenerating unit reduces (due to a lowering of density of the air), so isalso true when the airflow pressure is reduced. That is, as the airflowpressure is reduced, the power output is also reduced. Therefore, thepresent invention has eliminated the use of a cooling coil in the streamof the indirect evaporative cooling subsystem airflow 114 and 121 inorder to cool this air, and as a result, the pressure loss in the airstream 114 and 121 for the system remains constant as the air 114 and121 is discharged as air 123 through the air discharge housing 104 asthe useful dense air 116.

As illustrated in FIG. 5, the refrigeration system of the presentinvention cools the accumulated coolant within the sumps by circulatingthe coolant by a refrigeration pump 518 from the first stage sump 120via a coolant line 516 to a chiller-evaporator 506, where the coolant iscooled. The cooled coolant is than moved to the next stage sump 150 viaa coolant return line 520. As coolant is accumulated within the nextstage sump 150, any excess, additionally accumulated coolant within thenext stage sump 150 cascades down to the preceding sump 120 in thepreceding stage, as is described above in relation to FIG. 2.

The full cycle of the refrigerant system is comprised of an expansiondevice 504 where refrigerant in a liquid phase enters the expansiondevice 504 via refrigerant line 502, and is expanded into a low pressurevapor (or gas). Non-limiting examples of expansion devices that may beused with the present invention include capillary tubes, thermostaticexpansion valves, low-side float valves, a constant-pressure expansionvalve, or any other well-known expansion device appropriate for theintended use and the environment within which the present invention willbe used. The function of an expansion device 504 is to reduce thepressure of the liquid refrigerant (by changing its phase from liquid tovapor), and regulate the flow of refrigerant to the evaporator-chiller506. That is, the expansion device 504 throttles the flow of refrigerantinto the evaporator-chiller 506, changing the phase of the refrigerantfrom a liquid to gas (vapor). In other words, the expansion device 504allows the liquid refrigerant to have a controlled expansion, whichabsorbs ambient heat (latent heat) and to change its phase from liquidto gas. The now expanded vapor refrigerant inside the heat-exchangers ofthe chiller-evaporator 506 is a low temperature, low-pressurerefrigerant gas. The low temperature low pressure refrigerant absorbssensible heat within the tubes of the chiller-evaporator 506. As coolantis pumped by the coolant pump 518 into the chiller-evaporator 506, thecoolant comes into contact with the cooling coils, tubes, or other heattransfer mechanism of the chiller-evaporator 506, and is cooled byconductive heat transfer.

The refrigerant cycle continues by moving the low temperature gas (orvapor) refrigerant from the chiller-evaporator 506 via a compressorrefrigerant line 550 into the compressor 508 for compressing therefrigerant into a hot gas. The compression of the cool refrigerant gas(or vapor) coming from the chiller-evaporator 506 by the compressor 508increases refrigerant gas temperature due to heat of compression, whichis a well-known phenomenon.

The now hot gas refrigerant from the compressor 508 is moved viacondenser refrigerant line 510 into a set of condenser coils 514 firstin the first stage, and then 512 in the second stage, where the hightemperature gas refrigerant is cooled, condensed into liquid, and fedback to the expansion device 504 via the refrigerant line 502. Thepresent invention uses the wet side air of the direct evaporativecooling subsystem airflows 119 and 144, at essentially near a wet-bulbtemperature air, to cool the condensers 514 and 512, as the wet sideairflows are drawn up by a larger set of respective direct evaporativecooling subsystem fans 530 and 540.

It should be noted that the condenser refrigerant line 510 is coupledwith the condenser 514, and not with the condenser 512. This enables thehot gas refrigerant to move from within the condenser refrigerant line510 and into the condenser 514 for a first or preliminary stage cooling,which partially converts (or condenses) the gas into liquid. The nowcooler, hybrid gas-liquid refrigerant is moved to the secondary stagecondenser 512 for a secondary stage cooling, where the mixturegas-liquid refrigerant is further cooled and condensed into a liquidphase. The liquid refrigerant is then removed and recycled through line502 (which is coupled with condenser 512) and into the expansion device504, where the entire cycle repeats.

As a result of the refrigeration system of the present invention, theindirect evaporative cooling subsystem air 114 and 121 is further cooledand discharged through the air discharge housing 104 as cool, dense,useful air 116 without any pressure loss due to impediments (such as acooling coil) placed within their stream to cool the air 114 and 121.Further, the refrigeration cycle is maintained by the direct evaporativecooling subsystem air that flows within each stage of the multi-stagehybrid evaporative cooling system to cool the condenser portion of therefrigeration cycle, without much addition of energy to cool thecondenser.

FIGS. 6A and 6B are exemplary illustrations of a further embodiment fora multi-stage hybrid evaporative cooling system 600 in accordance withthe present invention, which use a vertical set of heat exchanges. Withthe system 600 of the present invention the direct evaporative coolingprocesses take place within the interior of the vertical heat exchangerchannels and the indirect evaporative cooling processes occur on theexterior of the vertical heat exchanger channels. In other words, theentire system 600 is the inside-out version of the above describedsystems in relation to FIGS. 1 to 5. With system 600, the wet air 119and 144 flow inside the vertical heat exchanger channels rather thanoutside, and the dry air 114 and 121, flow outside the vertical heatexchanger channels rather than inside. FIG. 6A shows a schematicperspective section of only a two-stage version for a multi-stage hybridevaporative cooling system 600 of the present invention, showing variousairflow paths. FIG. 6B is an exemplary schematic view of the two stagehybrid evaporative cooling system 600 that is illustrated in FIG. 6A,also showing various airflow paths. Each stage of the multi-stage hybridevaporative cooling system 600 illustrated in the exemplary FIGS. 6A and6B includes the same corresponding or equivalent components as eachstage of the multi-stage hybrid evaporative cooling system 100 that isshown in FIGS. 1 and 2, and described above. Therefore, for the sake ofbrevity, clarity, and convenience the general description of FIGS. 6Aand 6B will not repeat every corresponding or equivalent component thathas already been described above in relation to the multi-stage hybridevaporative cooling system 100 that is shown in FIGS. 1 and 2. Althoughnot shown, it will be readily apparent to those skilled in the art thatsystem 600 may include a single direct evaporative subsystem exhaust fan(as described and illustrated in FIG. 3), multiplicity of stages (asdescribed and illustrated in FIG. 4), and a refrigeration system (asdescribed and illustrated in FIG. 5).

The general use of vertical set of heat exchangers is described in U.S.Pat. Nos. 4,023,949; 4,107,940; and 4,418,527, all to Schlom et. al. Theentire disclosures of the U.S. Pat. Nos. 4,023,949; 4,107,940; and4,418,527 to Schlom et al. are incorporated herein by this reference,and the information incorporated herein is as much a part of thisapplication as filed as if the entire text and drawings of the U.S. Pat.Nos. 4,023,949; 4,107,940; and 4,418,527 were repeated in thisapplication, and should be treated as part of the text and drawings ofthis application as filed.

As illustrated in FIGS. 6A and 6B, the system 600 uses a verticallyoriented set of heat exchangers 612 for the first stage, and heatexchangers 640 and 642 for the second stage, with coolant sprayed ordelivered by other means inside the vertical heat exchanger channels.The direct evaporative cooling subsystem is accomplished by gravity flowof coolant downwardly along the inner surfaces of the vertical heatexchangers 612, 640, and 642 in conjunction with counter current flow ofdirect evaporative cooling subsystem air 119 and 144 flowing up withinthe vertical heat exchanger channels, and being exhausted by the fans124 and 154 for respective stages 1 and 2. The indirect evaporativecooling subsystem is accomplished by ambient air 110 flowing in thermalconductive contact with outer surfaces of the vertical heat exchangers612, 640, and 642 for cooling thereof, the cooled air 116 beingdelivered to other external systems.

As further illustrated in FIGS. 6A and 6B, the vertical set of heatexchangers 612, 640, and 642 are stacked between a top header 661, amiddle divider 663, and a bottom header 665 so as to form the indirectevaporative cooling subsystem (the dry side) enclosure. That is,indirect evaporative cooling subsystem enclosure is bounded on top bythe header 661, middle by the divider 663, the bottom by the bottomheader 665, the lateral enclosure walls 667, 669, and 671, and a frontand a back wall (not shown). The top header 661 is used for preventingflow of a coolant to within the indirect evaporative cooling subsystemenclosure. The at least one divider 663 is for maintaining separationbetween indirect evaporative cooling subsystem airflows, with the bottomheader 665 used for preventing flow of direct evaporative coolingsubsystem air 119 and 144 to within the indirect evaporative coolingsubsystem enclosure. The at least one divider 663 separates each stageof the multi-stage hybrid evaporative cooling system into two or morehorizontal sections for maintaining horizontal separation betweenindirect evaporative cooling subsystem airflows. This separation allowsthe indirect evaporative cooling subsystem airflows 114 and 121 througha first of the two or more horizontal sections to exit out of theindirect evaporative cooling subsystem enclosure and into the directevaporative cooling subsystem of a next stage. The separation alsoallows indirect evaporative cooling subsystem airflows through a secondof the two or more horizontal sections to continue within the indirectevaporative cooling subsystem enclosure into a next stage.

As further illustrated, the indirect evaporative cooling subsystem air114 and 121 flow freely outside the heat exchangers, and are cooledthrough conductive heat transfer with the heat exchangers 612, 640, and642. The direct evaporative cooling subsystem air 119 and 144 flows upinto the heat exchangers channels, exiting out of the heat exchangeropenings 673, and exhausted by the exhaust fans 124 and 154 of therespective first and second stage. Simultaneously, coolant is sprayed ordelivered by other mechanisms within the heat exchanger channels, withthe header 661 protecting the indirect evaporative cooling subsystemchamber from the coolant by directing the coolant to within the topopenings 673 of the heat exchangers 612, 640, and 642. As illustrated, afirst portion of the direct evaporative cooling subsystem within a nextstage substantially extends a vertical length of the stage, with asecond portion partially extending the vertical length of the stage,thereby facilitating a further cooling of a next stage indirectevaporative cooling subsystem.

As with other embodiments that are described and illustrated above, thedirect evaporative cooling subsystem of the multi-stage hybridevaporative cooling system 600 is also comprised of sumps 120 and 150within each stage for holding coolant. The coolant is provided to theheat exchangers by pumps 126 and 156 within each stage. The pumps 126and 156 move the coolant to distribution manifolds 134 and 160 fordelivery or spray of the coolant (through the spray nozzles or othercoolant distributing mechanisms 132 and 162) within the heat exchangerchannels. The direct evaporative cooling subsystem airflow within theheat exchanger channels evaporates the coolant flowing down within theheat exchanger channels for indirect evaporative cooling of an indirectevaporative cooling subsystem airflow exterior to the heat exchangerchannels through conductive heat transfer.

As further illustrated in FIGS. 6A and 6B, the second stage heatexchangers are comprised of an upper set of second stage heat exchangers640 that span a full horizontal length of the second stage, and arecapped by the header 661 at the top and the divider 663 at the bottom.The second stage heat exchangers are also comprised of a lower set ofsecond stage heat exchanges 642 that are capped by the divider 663 attheir top and the bottom header 665 at their bottom. The indirectevaporative cooling subsystem enclosure provides for a continuous flowof indirect evaporative cooling subsystem airs 114 and 121 from onestage to the next subsequent stage. Therefore, the indirect evaporativecooling subsystem air 114 flowing from the first stage within the upperhorizontal section (created by the divider 663) continuously flows intothe next stage as a much cooler air 121 and is exhausted through the airdischarge housing 104. The indirect evaporative cooling subsystem air114 flowing from the first stage lower horizontal section continuouslyflows over the lower vertical heat exchangers 642 and is cooled andexhausted into the second stage as cooler direct evaporative coolingsubsystem air 144.

As illustrated in FIGS. 6A and 6B, some of the indirect evaporativecooling subsystem (dry side) airflow 114 of the first stage heatexchangers 612 is exited and redirected over the lower set of the secondstage heat exchangers 642, and into the direct evaporative coolingsubsystem as second stage direct evaporative cooling subsystem air 144.The second stage direct evaporative cooling subsystem airflow 144 iscooler than the preceding stage airflow 119 because the second stagedirect evaporative cooling subsystem airflow 144 has already gone overthe first stage heat exchangers 612 as air flow 114, and therefore, hasbeen substantially cooled. In addition, in accordance with the presentinvention, the second stage direct evaporative cooling subsystem airflow144 has also traversed over the lower set of the second stage heatexchangers 642, which are cooler than the first stage heat exchangers612, the reasons for which are described below. Therefore, the airflowexiting out of the first stage and passing over the lower set of heatexchangers 642 is in fact cooler than the airflow over the precedingstage heat exchangers 612.

The lower set of any subsequent stage heat exchangers furtherfacilitates the evaporation of a lower temperature coolant to take placewithin the heat exchanger channels with a lower wet bulb temperatureair. This causes further reduction in the temperature of the indirectevaporative cooling subsystem air flowing over the heat exchangers 642,and into the subsequent stage. More specifically, and in relation toFIGS. 6A and 6B, the lower set of the second stage heat exchangers 642allows further evaporation of coolant at even lower temperature to takeplace within the lower set of the second stage heat exchangers 642. Thiscauses a further reduction in temperature of the indirect evaporativecooling subsystem airflow 114 before it emerges as the directevaporative cooling subsystem of the next subsequent stage (the secondstage), as direct evaporative cooling subsystem air 144.

In general, the lower set of any subsequent stage heat exchangers have alength of approximately equal to a vertical length of an upper set. Theactual number of channels that constitute a width of the lower set ofany subsequent stage heat exchangers is generally less than the numberof channels of the fully extended upper channels of the upper set of thesecond stage heat exchangers. That is, the number of channels of thelower set of any subsequent stage heat exchangers is less than thenumber of channels that constitute the upper set of any subsequent stageheat exchanges.

The much cooler direct evaporative cooling subsystem air 144 at thesecond stage passes over a second stage sump 150, and is subsequentlydrawn up and drawn out (referenced as 152) into the atmosphere by asecond stage direct evaporative cooing subsystem fan 154. The secondstage sump 150 further includes a second stage pump 156 that movescoolant stored within the second stage sump 150 through a second stagetube 158 to a second stage coolant distribution manifold 160. The secondstage coolant distribution manifold 160 is comprised of one or morenozzles or other coolant distributing mechanisms 162 through whichcoolant (such as water) is sprayed or delivered by other means, andcascades down the interior portion of the upper and lower set of secondstage heat exchangers 640 and 642 to cool down the interior channels ofthe upper and lower heat exchanger of the second stage. The second stagedirect evaporative cooling subsystem airflow 144 (or wet airflow) movingup within the heat exchangers of the second stage that contacts thecascading coolant, and facilitates the evaporation of the cascadingcoolant. This evaporation directly cools the interior of the heatexchanger channels, and indirectly cools the dense or useful airflow 121flowing over the upper and lower set of the second stage heat exchangers640 and 642. In other words, the wet side airflow within the secondstage heat exchanger channels causes the direct evaporation of thecoolant therein, and the dense side airflow 121 is cooled indirectly bythis evaporation through conductive heat transfer between itself and theexterior walls of the heat exchanger channels. The direct evaporativecooling subsystem air 144 moving up the second stage from within theinterior of the second stage heat exchanger channels facilitates thefurther evaporation of the cascading coolant therein at even lowertemperature within the interior of the second stage heat exchangers 640and 642. This evaporation directly cools air (due to latent heat) withinthe channels further, and indirectly further cools the indirectevaporative cooling subsystem air 121 through conductive heat transfer,flowing over both the upper and lower set of second stage heatexchangers 640 and 642.

As with other embodiments, the direct evaporative cooling subsystem iscomprised of exhaust units 124 and 154 (one for each stage or one unitfor the entire system as illustrated in FIG. 3) in the stage of themulti-stage hybrid evaporative cooling system for exhausting a directevaporative cooling subsystem airflow from the direct evaporativecooling subsystem. It further includes moisture eliminators 130 and 164in each stage of the multi-stage hybrid evaporative cooling system forremoving coolant droplets from the direct evaporative cooling subsystemairflow prior to exhausting the direct evaporative cooling subsystemairflow from the direct evaporative cooling subsystem. Coolant withinthe sump 150 of a final stage #2 of the multi-stage hybrid evaporativecooling system 600 is provided to a media pump 172, moving the coolantto a distribution system for distributing coolant along a top 180 and182 of a media 176, and 178 for further cooling and washing the indirectevaporative cooling subsystem airflow 123. As indicated above, themulti-stage hybrid evaporative cooling system 600 may include arefrigeration unit for further cooling of the direct evaporative coolingsubsystem air 116.

Although the invention has been described in considerable detail inlanguage specific to structural features and or method acts, it is to beunderstood that the invention defined in the appended claims is notnecessarily limited to the specific features or acts described. Rather,the specific features and acts are disclosed as preferred forms ofimplementing the claimed invention. Therefore, variations and alternateembodiments are contemplated, and can be made without departing from thespirit and scope of the invention.

1. A multi-stage hybrid evaporative cooling system, comprising: a directevaporative cooling subsystem within a stage of the multi-stage hybridevaporative cooling system; an indirect evaporative cooling subsystemwithin the stage of the multi-stage hybrid evaporative cooling system,with a portion of the indirect evaporative cooling subsystem within thestage of the multi-stage hybrid evaporative cooling system partiallyextending into a next stage thereby facilitating a further cooling ofthe next stage direct evaporative cooling subsystem.
 2. The multi-stagehybrid evaporative cooling system as set forth in claim 1, wherein: thedirect evaporative cooling subsystem is comprised of a sump within thestage of the multi-stage hybrid evaporative cooling system for holding acoolant that is provided to a set of heat exchangers within the stage ofthe multi-stage hybrid evaporative cooling system by a pump that movesthe coolant to a distribution manifold for delivery of the coolant on tothe heat exchangers, wherein a direct evaporative cooling subsystemairflow evaporates the coolant flowing down an exterior surface of theheat exchanger for indirect evaporative cooling of an indirectevaporative cooling subsystem airflow.
 3. The multi-stage hybridevaporative cooling system as set forth in claim 1, wherein: the directevaporative cooling subsystem generates a latent heat of evaporation,which causes a conductive heat transfer for the indirect evaporativecooling subsystem at a lower temperature, thereby lowering an indirectevaporative cooling subsystem airflow.
 4. The multi-stage hybridevaporative cooling system as set forth in claim 1, wherein: the directevaporative cooling subsystem is comprised of: an exhaust unit in thestage of the multi-stage hybrid evaporative cooling system forexhausting a direct evaporative cooling subsystem airflow from thedirect evaporative cooling subsystem; and a moisture eliminator in thestage of the multi-stage hybrid evaporative cooling system for removingcoolant droplets from the direct evaporative cooling subsystem airflowprior to exhausting the direct evaporative cooling subsystem airflowfrom the direct evaporative cooling subsystem.
 5. The multi-stage hybridevaporative cooling system as set forth in claim 4, wherein: theexhausted direct evaporative cooling subsystem airflow is directed toexternal systems for cooling of the external systems.
 6. The multi-stagehybrid evaporative cooling system as set forth in claim 1, wherein: thedirect evaporative cooling subsystem is comprised of: an exhaust unitfor exhausting a direct evaporative cooling subsystem airflow from thedirect evaporative cooling subsystem; and a moisture eliminator in thestage of the multi-stage hybrid evaporative cooling system for removingcoolant droplets from the direct evaporative cooling subsystem airflowprior to exhausting the direct evaporative cooling subsystem airflowfrom the direct evaporative cooling subsystem.
 7. The multi-stage hybridevaporative cooling system as set forth in claim 6, wherein: theexhausted direct evaporative cooling subsystem airflow is directed toexternal systems for cooling of the external systems.
 8. The multi-stagehybrid evaporative cooling system as set forth in claim 2, wherein:coolant within the sump of a final stage of the multi-stage hybridevaporative cooling system is provided to a media pump, moving thecoolant to a distribution system for distributing coolant along a top ofa media for further cooling and washing the indirect evaporative coolingsubsystem airflow.
 9. The multi-stage hybrid evaporative cooling systemas set forth in claim 8, wherein: the coolant from the media furtherlowers the temperature of the indirect evaporative cooling subsystem airflow due to further evaporation of the coolant; and the furtherevaporation of the coolant results in a lower dry bulb temperature,causing a further reduction of the temperature of the coolant in a mediasump, which when drained into the final stage sump, reduces atemperature of the coolant present within the final stage sump.
 10. Themulti-stage hybrid evaporative cooling system as set forth in claim 1,wherein the direct evaporative cooling subsystem is comprised of: arefrigeration unit for further cooling of the direct evaporative coolingsubsystem air.
 11. The multi-stage hybrid evaporative cooling system asset forth in claim 10, wherein a condenser coil of the refrigerationunit is positioned along a path of a direct evaporative coolingsubsystem airflow.
 12. The multi-stage hybrid evaporative cooling systemas set forth in claim 10, wherein the refrigeration unit is comprisedof: an expansion device for expanding a liquid refrigerant into a lowtemperature vapor refrigerant; an evaporator-chiller for lowering acoolant temperature using the low temperature vapor refrigerant from theexpansion device; a compressor for compressing the low temperature vaporrefrigerant from the evaporator-chiller to a high temperature gaseousrefrigerant due to heat of compression; and a condenser coil for coolingthe high temperature gaseous refrigerant from the compressor into amedium temperature liquid refrigerant, and fed to the expansion device.13. The multi-stage hybrid evaporative cooling system as set forth inclaim 10, wherein: a coolant from a first stage sump of one or morestages is moved by a pump into the evaporator-chiller for lowering atemperature of the coolant, and is moved to a last stage sump of one ormore stages; whereby excess coolant in the last stage sump is cascadeddown to a preceding stage sump, thereby lowering coolant temperature ofthe preceding stage sump.
 14. The multi-stage hybrid evaporative coolingsystem as set forth in claim 2, wherein: the heat exchangers arecomprised of a separate set of plates to form separate heat exchangersfor a stage, with independently created heat exchangers within eachstage aligned to form continuous channels for an airflow of the indirectevaporative cooling subsystem air from one stage to the next.
 15. Themulti-stage hybrid evaporative cooling system as set forth in claim 2,wherein: the heat exchangers are comprised of an upper set of platesthat span an entire horizontal length of all the stages of the hybridevaporative cooling system, and a lower of plates that partially span anentire horizontal length of each stage, with both the upper and thelower set of any subsequent stage heat exchangers being an extension ofa preceding stage heat exchangers.
 16. A multi-stage hybrid evaporativecooling system, comprising: an indirect evaporative cooling subsystemwithin a stage of the multi-stage hybrid evaporative cooling system; adirect evaporative cooling subsystem within the stage of the multi-stagehybrid evaporative cooling system, with a first portion of the directevaporative cooling subsystem substantially extending a vertical lengthof the stage, and a second portion partially extending the verticallength of the stage, thereby facilitating a further cooling of a nextstage indirect evaporative cooling subsystem.
 17. The multi-stage hybridevaporative cooling system as set forth in claim 16, wherein: theindirect evaporative cooling subsystem includes an indirect evaporativecooling subsystem enclosure for preventing an interchange of indirectevaporative cooling subsystem air pattern and direct evaporative coolingsubsystem air pattern, the indirect evaporative cooling subsystemenclosure, comprising: a top header for preventing flow of a coolant towithin the indirect evaporative cooling subsystem enclosure; at leastone divider for maintaining separation between indirect evaporativecooling subsystem airflows; a bottom header for preventing flow of adirect evaporative cooling subsystem air to within the indirectevaporative cooling subsystem enclosure.
 18. The multi-stage hybridevaporative cooling system as set forth in claim 17, wherein: the atleast one divider separates the stage of the multi-stage hybridevaporative cooling system into two or more horizontal sections formaintaining separation between indirect evaporative cooling subsystemairflows, thereby allowing the indirect evaporative cooling subsystemairflows through a first of the two or more horizontal sections to exitout of the indirect evaporative cooling subsystem enclosure and into thedirect evaporative cooling subsystem, and allowing indirect evaporativecooling subsystem airflows through a second of the two or morehorizontal sections to continue into the indirect evaporative coolingsubsystem enclosure within a next stage.
 19. The multi-stage hybridevaporative cooling system as set forth in claim 16, wherein: the directevaporative cooling subsystem is comprised of a sump within the stage ofthe multi-stage hybrid evaporative cooling system for holding a coolantthat is provided to a set of heat exchangers within the stage of themulti-stage hybrid evaporative cooling system by a pump that moves thecoolant to a delivery manifold for delivery of the coolant within theheat exchanger channels, wherein a direct evaporative cooling subsystemairflow within the heat exchanger channels evaporates the coolantflowing down within the heat exchanger channels for indirect evaporativecooling of an indirect evaporative cooling subsystem airflow exterior tothe heat exchanger channels.
 20. The multi-stage hybrid evaporativecooling system as set forth in claim 16, wherein: the direct evaporativecooling subsystem is comprised of: an exhaust unit in the stage of themulti-stage hybrid evaporative cooling system for exhausting a directevaporative cooling subsystem airflow from the direct evaporativecooling subsystem; and a moisture eliminator in the stage of themulti-stage hybrid evaporative cooling system for removing coolantdroplets from the direct evaporative cooling subsystem airflow prior toexhausting the direct evaporative cooling subsystem airflow from thedirect evaporative cooling subsystem.
 21. The multi-stage hybridevaporative cooling system as set forth in claim 20, wherein: theexhausted direct evaporative cooling subsystem airflow is directed toexternal systems for cooling of the external systems.
 22. Themulti-stage hybrid evaporative cooling system as set forth in claim 16,wherein: the direct evaporative cooling subsystem is comprised of: anexhaust unit for exhausting a direct evaporative cooling subsystemairflow from the direct evaporative cooling subsystem; and a moistureeliminator in the stage of the multi-stage hybrid evaporative coolingsystem for removing coolant droplets from the direct evaporative coolingsubsystem airflow prior to exhausting the direct evaporative coolingsubsystem airflow from the direct evaporative cooling subsystem.
 23. Themulti-stage hybrid evaporative cooling system as set forth in claim 22,wherein: the exhausted direct evaporative cooling subsystem airflow isdirected to external systems for cooling of the external systems. 24.The multi-stage hybrid evaporative cooling system as set forth in claim18, wherein: coolant within the sump of a final stage of the multi-stagehybrid evaporative cooling system is provided to a media pump, movingthe coolant to a distribution system for distributing coolant along atop of a media for further cooling and washing the indirect evaporativecooling subsystem airflow.
 25. The multi-stage hybrid evaporativecooling system as set forth in claim 24, wherein: the coolant from themedia further lowers the temperature of the indirect evaporative coolingsubsystem air flow due to further evaporation of the coolant; and thefurther evaporation of the coolant results in a lower wet bulbtemperature, causing a further reduction of the temperature of thecoolant in a media sump, which when drained into the final stage sump,reduces the temperature of the coolant present within the final stagesump.
 26. The multi-stage hybrid evaporative cooling system as set forthin claim 16, wherein the direct evaporative cooling subsystem iscomprised of: a refrigeration unit for further cooling of the directevaporative cooling subsystem air.
 27. The multi-stage hybridevaporative cooling system as set forth in claim 25, wherein a condensercoil of the refrigeration unit is positioned along a path of a directevaporative cooling subsystem airflow.
 28. The multi-stage hybridevaporative cooling system as set forth in claim 25, wherein therefrigeration unit is comprised of: an expansion device for expanding aliquid refrigerant into a low temperature vapor refrigerant; anevaporator-chiller for lowering a coolant temperature using the lowtemperature vapor refrigerant from the expansion device; a compressorfor compressing the low temperature vapor refrigerant from theevaporator-chiller to a high temperature liquid refrigerant due to heatof compression; and a condenser coil for cooling the high temperatureliquid refrigerant from the compressor into a medium temperature liquidrefrigerant, and fed to the expansion device.
 29. The multi-stage hybridevaporative cooling system as set forth in claim 25, wherein: a coolantfrom a first stage sump of one or more stages is moved by a pump intothe evaporator-chiller for lowering a temperature of the coolant, and ismoved to a last stage sump of one or more stages; whereby excess coolantin the last stage sump is cascaded down to a preceding stage sump,thereby lowering coolant temperature of the preceding stage sump. 30.The multi-stage hybrid evaporative cooling system as set forth in claim19, wherein the heat exchangers are comprised of a set of plates forminga vertical set of heat exchanger channels; with a first set of verticalset of heat exchanger channels spanning a substantial height of thestage of the hybrid evaporative cooling system, and a second set of thevertical set of heat exchangers channels spanning approximately half theheight of the of the hybrid evaporative cooling system.